In the near future an increasing demands of communication over wide distances, especially for example between continents and power supply cables to more inaccessible infrastructures will be needed. Hence, infrastructures, like sea cables and connectors linking sea cables and modules, e.g. subsea modules, like transformers, pumps etc., that are located and operated error proof subsea will be essential.
Subsea cables are normally handled subsea by a so called Remotely Operated Vehicle (ROV). Theses ROVs may impart so called snag loads on the cable during or after deployment subsea. Due to this, the cable can be pulled relative to the connector during handling, imparting a load which without suitable protection would result in damage to the termination portion of the connector, or even complete disconnection of the cable end from the connector. At this point retrieval of the cable and/or the connector is a very costly exercise. To minimize a risk of such a scenario subsea cables are equipped with a clamping unit or a cable grip, respectively, for positioning the cable in a wanted spatial arrangement, e.g. in respect to the connector. Moreover, such a grip ensures that different layers of the cable may keep their respective positions.
It is for example known to use a ‘passive’ clamp, in that once the clamp is assembled, the clamp components do not move. The load applied will change as environmental factors like temperature, pressure and subsequently stress-relaxation/compression-set of any of the components in that system alter the geometry of the critical components (not least of which being the cable itself). These geometry changes cause fluctuations in the pressure exerted by the fixed position clamp. These changes in the cable geometry (which occur after the grip has been assembled) cause the clamping force of the grip to reduce significantly, resulting in a compromised cable restraint system, and potentially damaging adjoining equipment. For example should the cable undergo expansion due to temperature rise, there is no scope for the passive clamp to allow for this change. Assuming the clamp was tightened to its full force at room temperature, the pressure exerted on the rubber cable as a result of thermal expansion is significant. The cable has no option but to deform under that pressure, and effectively flow from the high pressure region, causing the clamp to lose effectiveness as the volume of material it is acting on reduces, particularly if the temperature causing the expansion subsequently drops.